Advancements in digital communication technologies have permitted the development and deployment of many new types of communication devices. Communication systems in which communication devices are operable provide for the communication of data between sets of the communication devices. To ensure that operability of a communication device in a communication system, operating protocols and requirements are sometimes standardized, such as by a standard-setting body, and operation of a communication device in compliance with the operating standard ensures its operability with other communication devices that also operate in compliance with the standard.
Signaling protocols are regularly enumerated in such standards. Signaling protocols are used to set up communications between a set of communication devices to permit performance of a subsequent communication session. An SIP (Session Initiation Protocol) is an exemplary signaling protocol that is used pursuant to call set-up in IP (Internet Protocol)-based, and other packet data, communication schemes. Communication devices connectable to a packet data backbone, such as the Internet, that utilize SIP include, e.g., so-called, SIP phones. Such devices are peer-to-peer devices as they are capable of direct communications by way of the communication network without requiring that the communication network provide functionality other than, e.g., communication and routing of communication data.
The RFC 3261, for instance, sets forth operational requirements of the SIP pursuant to an establishment and maintenance of a dialog between a set of user agents. Typically, messages generated and communicated pursuant to the dialog between the user agents are communicated there between using a series of proxy hops through successive logical entities of the data network. The series of proxy hops is sometimes referred to as a route set. Messages are delivered to a user agent subsequent to the successive hops through the network. SIP messages include header parts having various header fields including, for instance, a contact header field. The RFC 3261 requires that the contact header fields of certain SIP messages to include URIs (Uniform Resource Identifiers) that are global. That is to say, the URIs must be able to be used at any element connected to the network. The RFC 3261 also mandates that the URIs be valid for requests sent outside of the dialog in which the contact URI is inserted. Exemplary SIP messages that include contact header fields populated with URIs include invite requests, register requests, and refer requests.
An IETF (Internet Engineering Task Force) draft standard proposal, the draft-IETF-SIP-GRUU, defines a type of URI, referred to as a globally routable user agent URI (GRUU). The GRUU has properties pertaining to routing to a user (Address of record) at a unique user agent and of being reachable from anywhere. Additionally, a new mechanism is defined in the draft standard by which an SIP user agent is able to obtain a GRUU from a SIP registrar of an SIP provider pursuant to registration. This mechanism thereby permits the URI to be used in the contact header fields of dialog-forming requests and responses in order to communicate the GRUU to other SIP user agents. Because a GRUU is provided by a user's SIP provider, the GRUU properties can be guaranteed by the provider. And, as a result, another SIP user agent is able to insert the GRUU in the request-URI of a SIP request targeted at the same specific AOR at a unique user agent instance in order to enable various applications, which require the GRUU property, including transfer and conferencing applications, to work reliably.
Existing schemes and protocols, however, fail to provide for user agent anonymity. For instance, when a call, i.e., a dialog, is established between a first user agent and a second user agent, and the call is to be transferred from the second user agent to a third user agent, the identity of the GRUU of the first user agent is ascertainable by the third user agent.
A mechanism is therefore required that provides for the creation of a GRUU that provides for persistence and provides a globally routable property but that also provides for anonymity.
It is in light of this background information related to SIP signaling and communications utilizing SIP that the significant improvements of the present invention have evolved.